The TEXT event cannot see things typed by the person where the script is loaded, so if you are using the same mirc as where the script is running, then the !open and !close are just duplicates. You could either delete them completely or change the event name from TEXT to something not valid like QTEXT to make it easy to enable them in the future.
Only if you have loaded the script onto a different mirc than the mirc you are using does the rest of this message matter to you.
You can alter the script by inserting a line to the TEXT event that responds to !open, so that it acts only if the message is from the correct nick. So if you want that even to respond only to nick kouyachi the first command of that event would be a line like:
if ($nick != kouyachi) return
If you want it to respond to the person using your host address regardless of your nick, you would first need to create the wildcard needed.
If you paste this in the edit box of the mirc where you will be typing, which is not the same mirc where the script is located:
//echo -a $address($me,2)
... this gives an address mask like *!*@your-exact-hostname
Instead of the above line checking if the nick is kouyachi, you would instead use the address you displayed above:
if (*!*@your-exact-hostname != $address($nick,2)) return
The nick portion of the address mask is where the asterisk is left of the "!", so it will match even if your nick is kouyachi_away or anything else.
If your address mask changes when you identify to network services, this will not work if you become un-identified.
If your hostname address changes because your ip-address changes sometimes, either because you are traveling or because your ISP changes your address sometimes, the line would need to be edited, but if you are always going to be the same nick, and nobody else is permitted to use that nick, you won't need to worry about making the script respond to the correct address instead of the correct nick.